m1  -m2  -m3
,


and so forth, where Einstein summation convention for the azimuthal
indices are applied, i.e., the indices
\(m_2^{\prime } = -l_2,-l_2+1,\ldots ,l_2-1,l_2\)  and
\(m_3^{\prime } = -l_3,-l_3+1,\ldots ,l_3-1,l_3\)  is summed over without the
summation symbols. With the above notation, the orthogonality
relations of the \(3j\) -symbols [1]} are represented by


(l l1l2)mm1m2
(l'l1l2)m'm'm1m2
= (-1)l+l1+l2 ll'2l+1
g(l)mm' l l1l2,
